Objective: Phenotypic switching of vascular smooth muscle cells (VSMCs) plays a critical role in atherosclerosis, vascular restenosis, and hypertension. Choline exerts cardioprotective effects; however, little is known about its effects on VSMC phenotypic switching and vascular remodeling. Here, we investigated whether choline modulates VSMC phenotypic changes and explored the underlying mechanisms. Approach and Results: In cultured VSMCs, choline promoted Nrf2 (nuclear factor erythroid 2-related factor 2) nuclear translocation, inducing the expression of HO-1 (heme oxygenase-1) and NQO-1 (NAD[P]H quinone oxidoreductase-1). Consequently, choline ameliorated Ang II (angiotensin II)-induced increases in NOX (NAD[P]H oxidase) expression and the mitochondrial reactive oxygen species level, thereby attenuating Ang II-induced VSMC phenotypic switching, proliferation, and migration, presumably via M3AChRs (type 3 muscarinic acetylcholine receptors). Downregulation of M3AChR or Nrf2 diminished choline-mediated upregulation of Nrf2, HO-1, and NQO-1 expression, as well as inhibition of VSMC phenotypic transformation, suggesting that M3AChR and Nrf2 activation are responsible for the protective effects of choline. Moreover, activation of the Nrf2 pathway by sulforaphane suppressed Ang II-induced VSMC phenotypic switching and proliferation, indicating that Nrf2 is a key regulator of VSMC phenotypic switching and vascular homeostasis. In a rat model of abdominal aortic constriction in vivo, choline attenuated VSMC phenotypic transformation and vascular remodeling in a manner related to activation of the Nrf2 pathway.
Conclusions: These results reveal that choline impedes VSMC phenotypic switching, proliferation, migration, and vascular remodeling by activating M3AChR and Nrf2-antioxidant signaling and suggest a novel role for Nrf2 in VSMC phenotypic modulation.
Keywords: angiotensin II; muscarinic agonists; myocytes, smooth muscle; oxidative stress; vascular remodeling.